1. Field of the Invention
The present invention relates to a display device and, more particularly, to a display device in a viewfinder for displaying various types of photographing information within the viewfinder in a photographing apparatus such as a camera and a video tape recorder.
2. Related Background Art
In order to display predetermined photographing information in a viewfinder in a photographing apparatus such as a camera and a VTR, LEDs and liquid crystal elements are arranged outside of the viewing frame. However, a user may miss an alarm display of overexposure or underexposure with this display mechanism. In addition, it is impossible to display an in-focus range and an optimal exposure range.
Although electronic cameras and VTRs and other "intelligent" apparatuses have been developed, novel information display devices in viewfinders have been rarely proposed. Demand has thus arisen for developing intelligent display devices which satisfy the user's needs. In association with the drawbacks of the conventional display devices in viewfinders, the present applicant proposes an overlying display arrangement wherein a liquid crystal display element is arranged in a field of view, i.e., the optical path of light reflected from an object to be photographed. For example, Japanese Patent Disclosure (Kokai) No. 52-110626 describes a display device in a viewfinder utilizing a TN (Twisted Nematic) liquid crystal display element. Since this display element normally uses a polarizing plate, the maximum light utilization efficiency obtainable is 50% so that the viewfinder is undesirably darkened. Japanese Patent Disclosure (Kokai) No. 58-62626 describes a display device in a viewfinder utilizing a GH (Guest-Host) liquid crystal display element. Although a polarizing plate can be eliminated from this display element, pigment molecules always absorb light. As a result, light utilization efficiency is degraded again, as in Japanese Patent Disclosure (Kokai) No. 52-110626, thus darkening the viewfinder. A hologram display device is also proposed. This display device is arranged in the optical path of light from an object to be photographed and is illuminated by an LED or the like. A shadow is formed by the hologram even in the nondisplay mode. Therefore, the hologram display device is not suitable for use as a display device in a viewfinder. In addition, it is impossible to perform versatile display of any numerical values by using the so-called 7-segment display elements.
The conventional display devices in viewfinders darken the viewfinders and form shadows therein, though such display devices can be conveniently used to display information in the field of view.